1. Field of the Invention
The present invention relates to a piezoelectric element with electrodes that is provided with electrodes and deforms according to a voltage applied thereto and to a head suspension employing the piezoelectric element.
2. Description of Related Art
Small-sized, precision information devices are rapidly advancing, and for use with such devices, needs for micro-actuators capable of conducting positioning control for very small distances are increasing. Such micro-actuators are highly needed by, for example, optical systems for correcting focuses and inclination angles, ink jet printers for controlling ink heads, and magnetic disk drives for controlling magnetic heads.
For the magnetic disk drives, an urgent task is to increase storage capacities. Increasing the storage capacity of a magnetic disk drive is generally achieved by increasing the storage capacity of a magnetic disk contained in the magnetic disk drive. The storage capacity or recording density of a magnetic disk will increase, without changing the diameter thereof, if the number of tracks per inch (TPI) on the magnetic disk increases, i.e., if the width of a track narrows. For this, a magnetic head of a head suspension installed in the magnetic disk drive must conduct precise positioning in a direction across the tracks, i.e., a sway direction. For realizing the precise positioning, an actuator capable of accurately moving and positioning the magnetic head in a very small range is needed.
To meet the need, the applicant of the present invention has proposed in Japanese Unexamined Patent Application Publication No. 2002-184140 a head suspension for a disk drive. The head suspension includes a base plate, a connection plate having a hinge thinner than the base plate, a load beam provided with a flexure, and a piezoelectric actuator having a pair of piezoelectric elements.
This related art employs a dual actuator system that involves, for precise positioning, a voice coil motor and the piezoelectric actuator having two piezoelectric elements made of, for example, PZT (lead zirconate titanate).
The piezoelectric actuator in the dual actuator system minutely moves a front end of the load beam in a lateral direction (sway direction) of the head suspension. Compared with a single actuator system employing only the voice coil motor, the dual actuator system is capable of more precisely positioning a magnetic head attached to a front end of the head suspension.
An important issue for the head suspension employing the dual actuator system is to protect the brittle piezoelectric elements from damage, prevent particles from dropping off the surfaces of the piezoelectric elements, and secure electric insulation between the head suspension body and the piezoelectric elements.
One approach to address the issue is disclosed in Japanese Unexamined Patent Application Publication No. 2002-184139 a head suspension for a disk drive. The head suspension includes an actuator base, an opening formed in the actuator base, and a piezoelectric element attached to the opening with a nonconductive adhesive. The nonconductive adhesive covers a circumferential end face of the piezoelectric element.
The head suspension of this related art is capable of protecting the piezoelectric element from damage, preventing particles from dropping off the surface of the piezoelectric element, and securing insulation between the piezoelectric element and the actuator base.
When attaching a piezoelectric element to an object such as a head suspension, it is very important to correctly orient the piezoelectric element. Generally, the piezoelectric element has polarity. If the piezoelectric element is reversely oriented and attached to the head suspension, the head suspension will deform opposite to an intended direction. This will cause serious troubles, and therefore, must be avoided.
Conventional piezoelectric elements, however, have no external appearances to indicate polarity. Accordingly, a misoriented piezoelectric element in a head suspension is frequently overlooked at the time of assembling until it is finally found in a finished-product test.